Method and apparatus for detecting a gas

ABSTRACT

The present invention relates to a sensor apparatus configured to detect the presence of a gas, such as a tracer gas and a leak detection apparatus configured to detect the presence of a tracer gas and indicate the location of a leak. The leak detection apparatus may further be configured to quantify the leak rate at the leak location.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to methods and apparatus to detect thepresence of a gas and in particular to methods and apparatus for thedetection of the presence of a tracer gas in a leak testing environment.

In traditional leak testing apparatus either an interior region or anexterior region of a part under test is placed at a higher pressure thanthe other of the interior region or exterior region of the part undertest. As such, if a leak is present in the part under test, the gas willflow from the higher-pressure side of the part under test to the lowerpressure side of the part under test. One method to monitor this flow ofgas and hence detect the presence of a leak is with a pressure decayapparatus which monitors the pressure of the higher-pressure side of thepart under test. A decrease in pressure could be an indication of aleak. Another method uses a mass spectrometry based apparatus to testfor the presence of a tracer gas on the lower pressure side of the partunder test. The tracer gas having been introduced on the higher-pressureside of the part under test.

Such apparatus provide the operator of the apparatus with an indicationof whether a part under test has a leak or at least whether the partunder test has a leak that exceeds a predetermined threshold value.Typically, the customer specifies the threshold value and the operatorsets the threshold value of the apparatus. If the operator of the leaktesting apparatus receives an indication from the leak testing apparatusthat the part under test contains an unacceptable leak, i.e. the leakexceeds the threshold value, the operator knows that the part under testis rejected and the operator places the part in a queue for furthertesting. However, the operator has no knowledge of the location of theleak or whether subsequently rejected parts are leaking fromapproximately the same location or a different location.

In order to determine the location of the leak further testing istraditionally required. Once the location of the leak is determinedchanges can be implemented to the manufacturing process to minimize thenumber of future rejected parts. The location of the leak is typicallydetermined in one of two methods. First, for larger leaks the locationof the leak is determined by pressurizing the rejected part andsubmerging the rejected part into a water bath. The location of the leakis determined based on the presence of air bubbles emanating from theleak site. Second, for smaller leaks the location of the leak can bedetermined by pressurizing the rejected part with a tracer gas andpassing a tracer gas detector, such as a sniffer apparatus, over thepotential leak areas of the rejected part. The tracer gas detector drawsthe gas proximate to a probe on the tracer gas detector apparatus, intothe probe, and past a detector to detect the presence of tracer gas. Onemethod of drawing the gas proximate to the probe is with a fan unit thatdraws gas into the probe and eventually past the detector. The leak siteis then noted and potentially changes to the manufacturing process willbe implemented.

The two stage process described above requires additional resources,delays the determination of the location of the leak for a given partunder test and delays the determination of whether the location of theleak is repeatable from rejected part to rejected part. Further, theabove two stage process is very operator dependent, in that the operatormust visually recognize the leak, denote the leak location, and subjecteach rejected part to a consistent testing procedure. Additionally,results vary from operator to operator in the ability of each operatorto recognize leaks and denote leak locations.

In addition, traditional apparatus often use mass spectrometry equipmentto detect the presence of a leak due to the need to detect smallquantities of the tracer gas. Such apparatus require that the gaslocated on the lower pressure side of the part under test be drawn to asensing element to analyze the gas to detect the presence of the tracergas.

As such, a need exists for a leak detection apparatus that provides anindication of the location of a leak in a part under test generallyconcurrently with the initial leak testing of the part. Additionally, aneed exists for a leak detection apparatus that provides an indicationof the location of a leak and an indication or measurement of the leakrate. Further, a need exists for a cost effective leak detectionapparatus.

In one exemplary embodiment, the present invention includes a leaktesting apparatus configured to detect the presence of a leak in a partunder test. The leak testing apparatus of the present invention in oneexample is further configured to determine the location of the leak inthe part under test. In another example the leak testing apparatus isfurther configured to determine both the location of the leak in thepart under test and the leak rate of the corresponding leak.

In another exemplary embodiment, an apparatus for detecting the presenceof at least one leak in a first region of a part under test and forlocalizing the location of the at least one leak, wherein a first sideof the first region contains a tracer gas and is at a higher pressurethan a second side of the first region such that the tracer gas willemanate through the at least one leak from the first side to the secondside comprises a plurality of sensors positioned proximate to the firstregion, each sensor being configured to detect the presence of a tracergas emanating from a leak and to provide a sensing signal; and acontroller connected to the plurality of sensors. The controllerconfigured to provide a leak detection signal in response to at least afirst sensor of the plurality of sensors detecting the presence of thetracer gas, the leak detection signal including leak detectioninformation representative of the location of the leak in the firstregion based on the sensing signals received from at least the firstsensor and a second sensor of the plurality of sensors. In one example,the apparatus further comprises an indicator configured to provide avisual indication of the location of the leak. In one variation, theindicator includes a display configured to display a firstrepresentation of the part under test and a sensor icon positioned onthe first representation, the sensor icon corresponding to a location ofa first sensor which is proximate to the location of the leak. Inanother variation, the indicator includes a display configured todisplay a first representation of the part under test and a leak graphicpositioned on the first representation, the position of the leak graphiccorresponding to a location of a first sensor which is proximate to thelocation of the leak.

In one exemplary method, a method of monitoring a part under test todetermine whether a first region contains a leak, the method comprisesthe steps of locating a plurality of sensors proximate to the firstregion, each of the plurality of sensors configured to detect thepresence of a tracer gas emanating from the leak and to provide asensing signal; monitoring each of the plurality of sensors to determineif the tracer gas is being detected by any of the plurality of sensors;and providing a leak detection signal in response to at least a firstsensor of the plurality of sensors detecting the presence of the tracergas, the leak detection signal including leak location informationrepresentative of the location of the leak in the first region based onthe sensing signals received from at least the first sensor and a secondsensor of the plurality of sensors. In one example, the method furthercomprises the step of providing a first indication of the location ofthe leak. In one variation, the first indication includes displaying ona display a first representation of a part under test and a sensor iconpositioned on the first representation, the sensor icon corresponding toa location of a first sensor which is proximate to the location of theleak. In another variation, the first indication includes displaying ona display a first representation of a part under test and a leak graphicpositioned on the first representation, the position of the leak graphiccorresponding to a location of a first sensor which is proximate to thelocation of the leak.

In yet another exemplary embodiment a computer readable media for use ina leak testing application to determine which of a plurality of sensorsis proximate to a leak in a part under test comprises a software portionconfigured to load a data file corresponding to the location of theplurality of sensors, to monitor the plurality of sensors to determineif any of the plurality of sensors has detected the presence of a leak,to determine the location of the leak if at least a first sensor of theplurality of the sensors detected the presence of the leak, and toprovide a visual indication of the location of the leak if at least thefirst sensor of the plurality of the sensors detected the presence ofthe leak. In one example, the software portion is further configured toprovide a first representation of the part under test and a first sensorrepresentation of the at least first sensor positioned on at least thefirst representation of the part under test. In another example, thevisual representation of the at least first sensor is a sensor icon. Inyet another example, the software portion is further configured todetermine the location of the leak by determining which sensor of theplurality of sensors detected the maximum concentration of a tracer gasemanating from the part under test. In still a further example, thesoftware portion is further configured to determine the location of theleak by determining which sensor of the plurality of sensors firstdetected the presence of a tracer gas emanating from the part undertest. In still yet a further example, the software portion is furtherconfigured to determine the leak rate of the leak in the part undertest. In one variation, the software portion further configured toprovide a leak graphic positioned on the first representation of thepart under test at a location proximate to the location of the leak.

In a further exemplary embodiment, the present invention includes asensor apparatus configured to detect the presence of a gas, such ashelium or hydrogen. In one example the sensor apparatus includes asensor controller and is a networkable sensor apparatus, such that thesensor apparatus is capable of sharing information with other devicesacross a network. In another example, the sensor apparatus is configuredto detect the presence and concentration of a gas, such as helium orhydrogen. In yet another example, the sensor apparatus is configured tobe incorporated into a component to detect the presence of a gas.

In yet a further exemplary embodiment, a sensor apparatus for detectingthe presence of a leak in a part under test, the part under test beingpressurized with a gas including a tracer gas comprises a housing; asensor configured to detect the presence of the tracer gas and togenerate a sensing signal; at least a first portion of the sensor beingcontained in the housing; and an I/O interface coupled to the housing,the I/O interface being configured to provide a first connectioncorresponding to an analog output and a second connection correspondingto a network output; and a sensor controller connected to the sensor andthe I/O interface and configured to generate an output signal based onthe sensing signal generated by the sensor, the sensor controllerfurther configured to determine if a network is present across thesecond connection of the I/O interface and to generate a data packet fortransmission over the network if the network is present, the sensorcontroller being contained in the housing. In one example, the sensorincludes a thermal conductivity transducer. In one variation, a portionof the thermal conductivity transducer is accessible from an exterior ofthe housing and is positioned proximate to the exterior of the housing.In another example, the sensor controller is configured to detect thepresence of a first network and the presence of at least one additionalnetwork. In one variation, the sensor controller is configured toprovide the analog output over the first connection when neither thefirst network nor the at least one additional network are present. Inyet another example, the sensor apparatus is a stand-alone leakdetection apparatus, the sensor apparatus further comprising a powersupply positioned within the housing and coupled to at least the sensorcontroller and an indicator viewable from the exterior of the housing,the indicator being configured to provide an indication of the presenceof the tracer gas.

In still a further exemplary embodiment, a gas sensor apparatus fordetecting the presence of a gas comprises a housing including a firstouter surface; a sensor configured to detect the presence of the gas andto generate a sensing signal, the sensor including a transducer portion,the transducer portion positioned proximate to the first outer surfaceof the housing such that the transducer portion is contactable by thegas; a sensor controller connected to the sensor and configured togenerate an output signal based on the sensing signal generated by thesensor; and wherein at least a portion of the sensor and the sensorcontroller are contained within the housing. In one example, the gassensor apparatus further comprises an I/O interface being coupled to thehousing and configured to connect the sensor controller to at least onedevice remote from the gas sensor apparatus. In one variation, theoutput signal of the sensor controller is a scaled analog output signalrepresentative of the amount of the gas detected by the sensor, thescaled analog output signal being made available to the at least oneremote device through a first connection of the I/O interface. Inanother variation, the output signal of the sensor controller is adigital signal representative of the amount of the gas detected by thesensor, the digital signal being made available to the at least oneremote device through a second connection of the I/O interface. In stillanother variation, the I/O interface further includes at least onetransceiver configured to receive the digital signal from the sensorcontroller and to generate and transmit a data packet containing thedigital signal. In another example, the gas sensor further comprises anindicator configured to provide a visible indication signal, the visibleindication signal being representative of the presence of the gas andthe visible indication signal being viewable from the exterior of thehousing.

In still another exemplary embodiment, a sensor apparatus for use with anetwork comprises a housing; a sensor configured to detect the presenceof a tracer gas and to generate a sensing signal, the sensor including afirst sensing portion, the first sensing portion being positioned suchthat the first sensing portion is contactable by the tracer gas; asensor controller connected to the sensor and configured to generate anoutput signal based on the sensing signal generated by the sensor; anetwork controller connected to the sensor controller and configured togenerate a network data packet, the network data packet includinginformation based on the output signal generated by the sensorcontroller; a network interface connected to the network controller andadapted to connect the sensor apparatus to the network; wherein thehousing is configured to contain at least a first portion of the sensor,the sensor controller and the network controller. In one example, thesensor includes a thermal conductivity transducer. In still anotherexample, the sensor apparatus further comprises an indicator coupled tothe sensor controller, the indicator including a first indicatorconfigured to provide status information related to the sensor apparatusand a second indicator configured to provide an indication of thepresence of the tracer gas.

Additional features of the present invention will become apparent tothose skilled in the art upon consideration of the following detaileddescription of the preferred embodiment exemplifying the best mode ofcarrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description of exemplary embodiments particularly refers tothe accompanying figures in which:

FIG. 1 is a diagrammatic representation of a leak testing apparatus ofthe present invention configured to test for a leak in a part under testhaving a first potential leak region;

FIG. 2 is a diagrammatic representation of the leak testing apparatus ofFIG. 1 configured to test for a leak in a part under test having atleast a first and a second potential leak regions;

FIG. 3 is a perspective view of a sensor array comprising a plurality ofsensors and a fixture whereto the plurality of sensors are affixed, theplurality of sensors being positioned adjacent a part under test havinga first potential leak region, the part under test being a torqueconverter and the first potential leak region being a weld joint;

FIG. 4A is a bottom view of the sensor array and the fixture of FIG. 3showing a sensing element of each of the plurality of sensors;

FIG. 4B is a perspective view of the sensor array and the fixture ofFIG. 3;

FIG. 5 is a perspective view of the sensor array, the fixture, and partunder test of FIG. 3 showing the sensor array and the fixture adjacentthe part under test;

FIG. 6 is a cross section of FIG. 5 along lines 6—6 showing thepositioning of a first sensor and a second sensor in the sensor arrayrelative to the position of the first potential leak region;

FIG. 7 is a flow chart of a first exemplary embodiment of leak testingsoftware, the leak testing software having a set up portion and aoperator portion;

FIG. 8 is a flow chart showing a first exemplary embodiment of the setup portion of the leak testing software of FIG. 7;

FIG. 9 is a flow chart showing a first exemplary embodiment of theoperator portion of the leak detection software of FIG. 7.

FIG. 10 is a flow chart of the first exemplary embodiment of a testingroutine of the operator portion of the leak testing software illustratedin FIG. 9;

FIG. 11 is experimental sensor output of the leak testing apparatus ofthe present invention, the experimental data related to a firstexemplary leak test showing the output data of five of the sixteensensors used in the leak test;

FIG. 12 is sensor output data of the sensors in a leak testing apparatusshowing the linear relationship of the average concentrations of tracergas measured by all of the sensors in a sensor array as a function oftime;

FIG. 13 a shows a plurality of example sensor icon overlaid on a pictureof a part under test;

FIG. 13 b shows the sensor icons of FIG. 13 a and an example of a leakgraphic overlaid on a picture of a part under test to provide avisualization cue of a leak emanating from the part under test at theposition of the leak graphic;

FIG. 14 is a diagrammatic representation of a dual mode sensor apparatusconfigured to detect the presence of a tracer gas;

FIG. 15 is a diagrammatic representation of a sensor apparatusconfigured to detect the presence of a tracer gas and to provide anoutput signal to a remote device;

FIG. 16 is a diagrammatic representation of a sensor apparatusconfigured to be a stand alone leak detector;

FIG. 17 shows an electronic schematic of a dual mode sensor apparatus ofthe present invention;

FIG. 18 is a perspective view of a thermal conductivity sensory elementfor use in a sensor apparatus, such as the sensor apparatus of FIGS.14–17;

FIG. 19 is a first perspective view of an exterior of the sensorapparatus of FIG. 17 incorporating the thermal conductivity sensor ofFIG. 18;

FIG. 20 is a second perspective view of the exterior of the sensorapparatus of FIG. 17 showing an indicator and an I/O interface;

FIG. 21 is a flowchart of a first exemplary embodiment of sensorsoftware for the sensor apparatus;

FIG. 22 is a flowchart of a first exemplary interrupt routine of thesensor software of FIG. 21;

FIG. 23 is a flowchart of a second exemplary interrupt routine of thesensor software of FIG. 21;

FIG. 24 is a flowchart of a third exemplary interrupt routine of thesensor software of FIG. 21;

FIG. 25 is a first perspective view of an exterior of a sensor apparatusshowing a sensing element accessible from the exterior;

FIG. 26 is a second perspective view of the exterior of the sensorapparatus of FIG. 25 showing an I/O interface; and

FIG. 27 is a diagrammatic representation of the sensor apparatus of thepresent invention incorporated as sensors in a component such as anautomobile.

DETAILED DESCRIPTION

While the invention is susceptible to various modifications andalternative forms, exemplary embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular forms disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

A Leak Detection Apparatus

Referring to FIG. 1, a diagrammatic representation of a leak testingapparatus 100 according to the present invention is shown. Leak testingapparatus 100 includes a test region 102, a plurality of sensors 106 (ofwhich sensors 106 a and 106 b are shown for illustration), a controller108, and an indicator 110. Although only two sensors, 106 a and 106 bshown in FIG. 1, it is contemplated that plurality of sensors 106includes two, three or more sensors. Test region 102 is configured toreceive a part under test 112 having at least a first potential leakregion 114. Example potential leak regions include weld regions andjoints. However, in one example the entire surface of a part under testor a portion thereof may be tested for potential leaks and therefore theentire surface or portion thereof may be considered a potential leakregion. In one example, test region 102 includes at least one fixture(not shown) configured to hold part under test 112 and configured toposition the plurality of sensors 106 relative to potential leak region114 of part under test 112. In another embodiment, test region 102further includes a pressure chamber (not shown). The pressure chamberbeing configured to pressurize a volume of air around part under test112.

In the illustrated embodiment, controller 108 includes a computer 116and a programmable logic controller (PLC) 118. Computer 116 isconfigured to process data received from the plurality of sensors 106,identify the location of a leak, provide a signal to indicator 110 ofthe location of the leak, and to provide for the ability of the leakdata to be stored for future analysis. In another embodiment, computer116 is further configured to quantify the leak rate of the leak and toprovide a signal to indicator 110 of the leak rate. An exemplarycomputer 116 is an EMAC Industrial computer available from EMAC, Inc.located at P.O. Box 2042, Carbondale, Ill. 62902.

PLC 118 is configured to control the physical motions of leak testingapparatus 100. An exemplary PLC 118 is a Model No. SLC 5/05 availablefrom Allen Bradley through Rockwell Automation located at US BankCenter, 777 East Wisconsin Avenue, Suite 1400 Milwaukee, Wis. 53202. Inone example, PLC 118 is configured to actuate components, such ascylinders, to secure part under test 112 in the corresponding fixture orfixtures of test region 102 configured to secure part under test 112 andto position plurality of sensors 106 a and 106 b proximate to potentialleak region 114. PLC 118 is further configured to control the fillingand evacuating of the part under test 112 with a tracer gas. In analternative embodiment PLC 118 is configured to control the filing andevacuating of the pressure chamber of test region 102 with a tracer gas.The use of a PLC to control the filing and evacuating of the part undertest with a tracer gas, such as PLC 118, is well known in the art.

PLC 118 is further connected to a human-machine interface (HMI) 119. HMI119 provides an exemplary interface for the operator of leak testingapparatus 100 to input parameter values to leak testing apparatus 100,such as a setpoint or leak rate which corresponds to an unacceptableleak in the part under test and/or a test timer value to control thelength of a test cycle for part under test 112. An exemplary HMI is aPanelview standard terminal from Allen Bradley through RockwellAutomation located at US Bank Center, 777 East Wisconsin Avenue, Suite1400 Milwaukee, Wis. 53202. In the illustrated embodiment HMI 119 islinked to controller 108 through a network, such as network 120discussed below. In an alternative embodiment, HMI 119 is directlyconnected to controller 108.

In another embodiment PLC 118 is provided parameter values across anetwork, such as network 120, from computer 116 or from a remotecomputer (not shown). In a further embodiment PLC 118 is providedparameter values from a computer readable media (not shown) removablycoupled to PLC 118 or computer 116 or a remote computer (not shown).

In one embodiment of leak testing apparatus 100, PLC 118 is furtherconfigured to perform an initial knock-out or gross leak test on partunder test 112, such as a pressure decay test. It is well known in theart to use a PLC, such as PLC 118, to perform a pressure decay test on apart under test. If part 112 fails the gross leak test then the partunder test 112 does not need to be tested with the more accurate tracergas or fine leak test described below unless it is desired to pin-pointthe location of the gross leak. In one variation, the gross leak test,such as the pressure decay test is conducted simultaneously with thefine leak test. When a pressure decay test and the fine leak test areconducted simultaneously, the pressure decay test uses a gas containingthe tracer gas.

In the illustrated embodiment, computer 116 and PLC 118 are linkedtogether through network 120. Network 120 is configured to permitcomputer 116 and PLC 118 to share information. Exemplary networksinclude wired networks, wireless networks, such as an RF network, an IRnetwork, or a cellular network, local area networks, such as an Ethernetnetwork or a token ring network, wide area networks, a controller areanetwork (CAN), connections to the Internet or an Intranet, a RS232connection, an RS485 connection, or other suitable networks or methodsof connecting computer 116 and PLC 118. Computer 116 and PLC 118 can beconnected to additional devices across network 120, such as remotecomputers (not shown) in quality control or to control devicespositioned at various stations in the manufacturing process of partunder test 112. As such, feedback can be instantly provided to qualitycontrol personnel or manufacturing personnel concerning the location ofleaks in rejected parts and of any correlation between the leaklocations of the rejected parts.

In an alternative embodiment, controller 108 is comprised of a singlecomputer, such as computer 116 which is configured to perform theabove-described functions of both computer 116 and PLC 118. In oneexample, HMI 119 is a touch screen, a light pen, a mouse, a roller ball,or a keyboard.

As stated earlier, for a fine leak test, controller 108 is configured toprovide a gas including a tracer gas to either an interior of part undertest 112 or an exterior of part under test 112. It is well known in theart to seal a part under test so that the tracer gas is retained oneither the interior or exterior of part under test 112 in the absence ofa leak in part under test 112. If the tracer gas is provided to theinterior of the part under test then test region 102 does not require apressure chamber while if the tracer gas is provided to the exterior ofthe part under test 112 then the test region 102 includes a pressurechamber (not shown) to permit the exterior of the part under test 112 tobe pressurized.

The tracer gas is introduced to either the interior or the exterior ofpart under test 112 such that the interior or exterior including thetracer gas is at a higher pressure relative to the other of the interioror exterior not including the tracer gas. Therefore, a pressuredifference is created between the interior of part under test 112 andthe exterior of part under test 112, the higher pressure regioncorresponding to the region containing the tracer gas. As such, if partunder test 112 includes a leak, the tracer gas will emanate or flow fromthe higher pressure region to the lower pressure region. In one examplethe tracer gas is helium. In another example the tracer gas is hydrogen.

Leak testing apparatus 100 is configured to detect the presence of aleak in part under test 112, as indicated by the presence of the tracergas in the lower pressure region. Leak testing apparatus 100 is furtherconfigured to run a leak test whereby part under test 112 is monitoredfor leaks for a time period corresponding to a value of the test timerprovided to PLC 118. As shown in FIG. 1, sensors 106 are placedproximate to potential leak region 114. As stated before it iscontemplated to position more than two sensors 106 proximate to region114. Sensors 106 are connected to controller 108 and are configured toprovide a sensing signal, representative of the detection of the tracergas. In one example the sensing signal is proportional to theconcentration of the tracer gas. In the illustrated embodiment, sensors106 a and 106 b are connected to controller 108 over a network 122,network 122 being generally similar to network 120, such that sensors106 a and 106 b each generate a sensing signal and provide the sensingsignal to controller 108 across network 122 as a network message or datapacket. In one example network 122 and network 120 are portions of thesame network. In an alternative embodiment, the sensors 106 areconnected to controller 108 directly such that controller 108 receives asensing signal from each sensor as a direct input, such as an analogsignal.

Controller 108 is configured to receive the sensing signals from sensors106 and to determine if the sensing signals indicate that a leak ispresent in part under test 112. As explained in more detail below, thelocation of the leak can be deduced by monitoring the individual sensingsignals from sensors 106. Further, as explained in detail below, if thesensors define an area of containment or accumulation volume the leakrate of leak can be deduced or quantified by monitoring the aggregatesensing signals, such as the sensing signals from both sensors 106.

Indicator 110 is connected to controller 108 and configured to providean indication signal to an operator of leak testing apparatus 100 of thepresence and location of a leak in part under test 112. Controller 108is configured to provide a leak detection signal to indicator 110 inresponse to at least one of sensors 106 a and 106 b detecting thepresence of the tracer gas. Further, the leak detection signal ofcontroller 108 can be provided to other devices such as a remotecontroller (not shown). The leak detection signal including informationrepresentative of the location of the leak and/or information related tothe leak rate of the leak.

In the illustrated embodiment indicator 110 is directly connected tocontroller 108. In another embodiment, indicator 110 is linked tocontroller 108 over a network, such as network 120. Example indicationsignals include a signal to a network device containing the location ofthe leak, an audio message, a visual text message of the location of theleak, or a visual image of the part under test with a leak graphicplaced at the location of the leak. In one embodiment, indicator 110 isfurther configured to provide an indication of the leak rate of theleak. The indication of the leak rate can be included in the same signalas the location of the leak or sent in a second indication signal.

Referring to FIG. 2, a leak testing apparatus 100′ is shown in aconfiguration for monitoring a part under test 212 having at least twopotential leak regions 214 a and 214 b. Leak testing apparatus 100′ isgenerally similar to leak testing apparatus 100. As such, like numeralsare used for components that are common to both leak testing apparatus100 and leak testing apparatus 100′. As shown in FIG. 2, a first sensorarray 224 a comprising a plurality of sensors such as sensors 106 a and106 b is positioned proximate to a first potential leak region 214 a anda second sensor array 224 b comprising a plurality of sensors such assensors 206 a, 206 b, 206 c, 206 d, 206 e, 206 f, and 206 g ispositioned proximate a second potential leak region 214 b. Sensors 206a–g are generally identical to sensors 106 a and 106 b. Each sensorarray 224 a and 224 b is connected to controller 108. As stated abovethe sensors are connected to controller 108 either through a network,such as network 122 or directly.

In one embodiment sensor arrays 224 a and 224 b simply denote the sensorgrouping, sensors 106 a and 106 b and sensor 206 a–g, respectively. Inanother embodiment sensor arrays 224 a and 224 b correspond to networkdevices configured to relay network traffic from the respective sensorsto other network components, such as controller 108. In one example,sensor arrays 224 a and 224 b are network routers. In yet anotherembodiment, sensor arrays 224 a and 224 b are controllers and areconfigured to receive data from the respective sensors and to compilenetwork messages to other network devices based on the data receivedfrom the respective sensors. In one example the respective sensors arelinked to the sensor array controllers through a network similar tonetwork 122. In another example the respective sensors are directlyconnected to the sensor array controllers and provide an analog output.The network messages compiled by the sensor array controller may be therelaying of signals from the respective sensors, an indication of a leaklocation, or an indication of the leak rate of a leak.

Although the present invention may be practiced with a single sensorpositioned proximate to region 214 a and a single sensor positionedproximate to region 214 b, the more sensors that are positionedproximate to either potential leak region 214 a or 214 b the greater theaccuracy of leak detection apparatus 100′ in determining the location ofthe leak and/or the quantification of the leak rate. As such, it ispreferred to connect sensors 206 a–g, 106 a and 106 b to controller 108through a network because such a connection allows for many sensors tocommunicate with controller 108 without requiring that controller 108 tohave a multitude of data inputs, only access to a network.

Referring to FIG. 3, an exemplary sensor array 130 includes a pluralityof sensors 132 a–l. Sensor array 130 is configured to be used with leaktesting apparatus 100 or with leak testing apparatus 100′. As shown inFIG. 4 a, each sensor 132 a–l includes a sensing element or transducer134 a–l. In a preferred embodiment sensors 132 a–l are configured tointerface with a network, such as a Controller Area Network (CAN)network or an RS-485 network. An exemplary sensor for use over either aCAN network or an RS-485 is sensor 300 shown in FIGS. 14–24 below. Asexplained below, in connection with sensor 300, sensing element ortransducer 134 a–l of sensor 132 a–l is configured to detect thepresence of the tracer gas when the tracer gas is in contact withsensing element or transducer 134 a–1 . Although sensor 300 as describedbelow is capable of functioning in both an analog mode and a networkmode, it is to be understood that sensors 132 a–l in the preferredembodiment need only to be capable of functioning in the network modeand further only need to be configured for one network, such as eitherRS-485 or CAN. In alternative embodiments, sensors 132 a–l areconfigured for two or more networks.

Sensors 132 a–l of sensor array 130 are affixed in a fixture 133 suchthat sensor array 130 is easy to position relative to a potential leakarea of a part under test, such as a weld 134 of torque converter 136shown in FIGS. 3, 5 and 6. Fixture 133 is configured to position sensors132 a–l proximate to weld 134 of torque converter 136 in a repeatablefashion such that sensor 132 a is always placed next to portion 138 ofweld 134. As such, if a leak is present in portion 138 of weld 134 in afirst torque converter 136 and a subsequent torque converter 136 thesame sensor, sensor 132 a, will be denoted as being proximate to theleak.

As shown in FIGS. 3, 4 a, 4 b, 5 and 6, fixture 133 is configured todefine in cooperation with part 134 an interior region or accumulationvolume 140 (shown in FIG. 6) wherein any emanating tracer gas from aninterior region 142 of part 136 through a leak such as leak 144 in weld134 will be collected. The emanating tracer gas is collected withininterior region 140 such that the change in concentration of the tracergas over time may be monitored to quantify the leak rate of the leak. Inone example, interior region 142 is not a sealed region, in order toprevent a pressure buildup in interior region 142 and hence a slowing ofleak 144 which could lead to an inaccurate calculation of thecorresponding leak rate.

In an alternative embodiment, the fixture for securing the sensor arraysupports the sensors and positions the sensors repeatably in relation tothe potential leak region. However, the fixture does not define aninterior region wherein emanating tracer gas collects. As such, thefixture does not permit an accurate estimate of the leak rate only anindication of the location of the leak relative to the potential leakregion.

Referring to FIG. 6, sensor 132 f is positioned proximate to leak 144.As such, sensing element 134 f will detect the presence of the tracergas emanating from leak 144 before sensing element 134 a of sensor 132 awill detect the presence of the tracer gas. Further, over time sensor132 f will have a maximum response compared to sensor 132 a meaning thatsensor 132 f will detect a higher concentration of the tracer gas thansensor 132 a. As explained below, one or both of these facts is used todetermine the location of leak 144. Further, as explained below thesummation and average of the response of all sensors 132 a–l is used todetermine the leak rate associated with leak 144 when the geometry offixture 133 is such that the tracer gas emanating from leak 144 isgenerally retained in interior region 140.

Referring to FIGS. 7–10, an exemplary embodiment of a leak testingsoftware 600 is shown. Leak testing software 600 is configured to beexecuted by controller 108 in association with a fine leak test. Forexample, for the testing of part 136 of FIGS. 3, 5, and 6, software 600is configured to associate sensor array 130 and sensors 132 a–l relativeto test part 136, to monitor signals provided by sensors 132 a–l over anetwork, such as network 122, and to provide an indication of thelocation of leak 144 and/or to provide an indication of the leak rateassociated with leak 144. In one example, controller 108 as a leakdetection signal provides the indication of the location of leak 144and/or the leak rate of leak 144. It is contemplated that software 600is configured to monitor multiple sensor arrays. In the illustratedembodiment shown in FIGS. 7–10, leak testing software 600 is executed bycomputer 116 and receives information from and sends information to PLC118. In an alternative embodiment, leak testing software 600 ispartially executed by computer 116 and partially executed by PLC 118. Inyet a further alternative embodiment at least a portion of thefunctionality of software 600 is provided as firmware. In anotheralternative embodiment, software 600 is executed by a remote computerand commands are provided to controller 108 over a network, such asnetwork 120.

In one embodiment, software 600 is available as one or more files on aportable computer readable media, such as a diskette, a CD-Rom, a Zipdisk, a tape, a memory card, or a flash memory card. Software 600 in oneexample includes an installation program configured to load software 600on computer 116 and/or to configure software 600. In an alternativeembodiment, software 600 and/or an installation program is availableacross a network as one or more downloadable files.

Referring to FIG. 7, leak testing software 600 includes a setup portion602 configured to allow an operator to set a variety of parametersrelated to a particular job, such as the testing of a particular partunder test, for instance part 136, and a operator portion 604 configuredto be used by the operator preparing to leak test a part. Operatorportion 604 is configured to load the parameters set for a particularpart under test and to execute a testing routine 656 to test a firstpart for a leak.

Referring to FIG. 8, an exemplary setup portion 602 of software 600 isshown. As represented by block 606, at least a first picturerepresentative of the part to be tested is loaded. The picture is usedto provide a visual indication to the operator of the location of theleak. In a first example, the picture corresponds to a still image of aphysical part. In a second example, the picture corresponds to a viewproduced from an electronic database of the part such as a CAD softwarepackage. In a third example, the picture corresponds to a threedimensional solid model of the part produced from an electronic databasesuch as a CAD software package.

As represented by block 608, the operator places a representation of asensor, such as sensor 132 a, on the picture of the part to be tested.In one embodiment the representation of the sensor is a sensor icon, seeFIG. 13 a for an example sensor icon such as sensor icon 135 a. Thesensor icon shown in FIG. 13 a is a triangular shape. However, it iscontemplated that the sensor icon could be a variety of shapes and couldinclude text such that a sensor number and/or sensor name is displayed.The location of sensor 132 a on the picture corresponds to the locationof the physical sensor 132 a relative to part 136 during the testing ofpart 136. However, updating the location of sensor 132 a on the picturedoes not move the location of sensor 132 a on the physical part. Thelocation of sensor 132 a on the picture is simply a representation ofthe location of sensor 132 a on the physical part. The operator thenupdates the information related to sensor 132 a, as represented by block610. Example sensor information to be updated includes a name for sensor132 a, a network id for sensor 132 a, sensor position data, which sensorgroup or array 130 sensor 132 a is associated with, and a displaypriority for sensor 132 a or the picture currently displayed. Thedisplay priority is a parameter associated with the preferred view toshow a leak emanating from sensor 132 a. In the case of a picture thedisplay primary parameter indicates the default view to use duringoperator portion 604.

Software 600 queries whether additional sensors are to be displayed onthe current picture of the part to be tested, as represented by block612. If additional sensor locations are visible in the current picture,the operator selects yes and repeats the above process for theadditional sensors. If additional sensors are not visible in the currentpicture, the operator should select no which leads software 600 to querywhether additional pictures of the part to be tested are to be loaded,as represented by block 614. If additional pictures are to be loaded,the operator selects yes and software 600 will loop back to block 606.Otherwise, the operator is prompted to save the sensor mapping filecorresponding to the part to be tested, as represented by block 616. Thesensor mapping file includes the information entered during the setupportion 602. In one example, the sensor mapping file is a text filewhich includes at least references to the pictures of the part to betested, the sensors included on each picture, the sensor positions foreach picture and the sensor parameters for each picture.

Turning to FIG. 9, operator portion 604 of software 600 is shown. Asrepresented by block 620, the operator upon initiating operator portion604 enters or selects the location of the directory containing thesensor mapping file corresponding to the current part under test, suchas part 136. If the operator does not select a proper path the operatoris again required to enter or select the directory, as represented byblock 622. Otherwise, if a proper path is selected, the operator nextselects the correct sensor mapping file 616, as represented by block624.

The sensor mapping file is loaded into a memory of controller 108 andthe operator is presented with a list of pictures of the part under testcontained within the sensor mapping file, as represented by block 626.The operator selects a picture from the list and the selected picturealong with the sensor icons 135 are displayed on a correspondingdisplay, as represented by blocks 628 and 630. By having the operatorselect a picture for viewing, a visual check can be done by the operatorto insure that the selected sensor mapping file corresponds to the partto be tested.

At this point the operator can make changes to the sensor information orsensor placement or proceed to begin testing, as represented by block632. If updates are required the operator selects the sensor to beupdated, as represented by block 634. The operator can update theplacement of a selected sensor by manually inputting new positioninformation or by moving the corresponding sensor icon 135 relative tothe picture of the part. However, the user is only changing the positionof the sensor on the picture not the actual physical sensor location.Either way the new sensor position is received and the sensor table isupdated, as represented by blocks 636, 638, and 640. Further, theoperator can update the sensor information, such as display priority,sensor name, or sensor network id, as represented by blocks 642, 644,and 646. In one example, the sensor information must be updated when abroken sensor is replaced with a new sensor having a different networkid.

The operator can now select another sensor and update either the sensorposition or sensor information associated with that sensor, asrepresented by block 648. If an additional sensor is selected the abovedescribed process related to blocks 636, 638, 640, 642, 644, and 646 isrepeated. Once the updates have been made to the positions of thesensors or the sensor information, the operator must either save thechanges to the sensor mapping file or discard the changes, asrepresented by block 650. If the changes are saved, software 600 querieswhether to initiate a testing routine, as represented by blocks 652,654, and 656. If the changes are discarded the operator is againpresented with the option of updating the sensor position or sensorinformation, as represented by block 632.

As represented by blocks 654, 656, 658, 660, and 662, once the updateshave been made to the displayed picture, the operator can either beginthe testing routine, block 656, exit the program, block 660, select anew sensor mapping file, blocks 662 and 620, or select an additionalpicture associated with the current sensor mapping file, block 662, 626,and 628. The operator, in one example would select an additional pictureassociated with the sensor mapping file to update the sensor placementor sensor information of a sensor not visible in the previous displayedpicture. Further, in one example, the software recognizes sensorposition changes or sensor information changes in a first picture andupdates the corresponding sensor position or sensor information for theadditional pictures including the sensor.

Referring to FIG. 10, an example testing routine 656 is shown. Asrepresented by blocks 664 and 665, when a testing routine is initiatedthe selected sensor mapping file is loaded, block 664, and theassociated part images or pictures are loaded, block 665. One of thepart images has a parameter value designating that part image as adefault part image. The default part image is shown on the display, asrepresented by block 668. The display of a default image provides avisual cue to the operator that software 600 has loaded the correctsensor mapping file and the corresponding part images.

Software 600 waits for a start test signal from the PLC indicating thatthe part under test is ready for testing, as represented by block 670.In one example, the signal from the PLC corresponds to the situationwherein part under test 136 has been properly positioned in test region102, sensors 132 are all in the correct positions, the tracer gas hasbeen properly introduced and the pressure difference between theexterior and interior of the part under test has been established. Oncethe start test signal is received from PLC 118, a command is issued toall sensors 132 to monitor for the presence of the tracer gas, asrepresented by block 672, and a test timer is initiated, as representedby block 674. The test timer defines the length of the test for part136. If a leak is not detected in part 136 during the length of the testtimer part 136 is approved. In one example of testing routine 656,testing routine either upon the detection of a leak or expiration of thetest timer is reset to begin testing on a second part, wherein thesecond part is generally identical to part 136. As such, once theoperator enters testing routine 656, the operator does not have to cyclethrough the additional prompts of operator portion 604, such as blocks620, 624 and 628 before testing the second part.

As represented by block 676, the software monitors network 122 todetermine if data is received from a sensor 132 or other component onnetwork 122. If data is received across network 122, the determinationis made whether the data corresponds to a detection of the tracer gas,as represented by block 678. In one example, the determination isdependent on whether the amount of tracer gas detected exceeds athreshold value set by a parameter in the sensor mapping file. If thedata does not corresponds to the detection of the tracer gas, the testtimer is checked to determine if the testing procedure is complete, asrepresented by block 680. An example instance of data not correspondingto the detection of the tracer gas includes sensor status data, such assensor 132 is operating properly or that an error has occurred.

If the data does correspond to the detection of the tracer gas, then thedata and subsequent data is analyzed, as represented by block 685. Thedata is analyzed to determine the location of the leak, as representedby block 686, a localization routine. In one embodiment, the data isfurther analyzed to determine the rate of the leak, as represented byblock 688, a leak rate routine. Leak rate routine 688 is executedgenerally simultaneous with localization routine 686. Both localizationroutine 686 and leak rate routine 688 provide information to generate anindication of a leak in part 136, such as a visualization of the leak ona picture or image of the test part to easily allow the operator to notethe location and size of the leak. For example, a leak graphic 137 asshown in FIG. 13B to represent the detection of a leak by sensor 132 f.Additional indications of the leak include a signal sent by controller108 to a remote device, such as a computer in quality control or in themanufacturing area, a visual text message on the HMI unit associatedwith PLC 118, an audible alarm, or a visual cue such as a flashinglight.

Localization routine 686 determines the location of the leak by findingthe sensor which is detecting the largest concentration of the tracergas, as represented by block 690. The location of the leak is correlatedto the location of this sensor, as represented by block 692. The pictureof part 136 that provides the optimal viewing of the location of theleak is automatically selected and displayed along with an indication ofthe leak location, as represented by block 694. The picture to displayis based on the display preference set for the sensor in the sensormapping file. In a first example, flashing the corresponding sensor iconor changing the color or other attribute of the corresponding sensoricon is a visual cue of the leak location. In a second example, as shownin FIG. 13B, the leak location is shown by leak graphic 137 representingthe emanating of the tracer gas from the leak location. In a furtherexample, the leak graphic of FIG. 13B is an animated graphic such thatthe graphic simulates gas emanating from the leak location. In yet afurther example, the leak graphic flashes to further indicate thelocation of the leak. Both exemplary sensor icons and leak graphics areshown in FIG. 13B.

In an alternative embodiment, the location of the leak is determined bythe sensor which was the first to detect the tracer gas. In a furtheralternative embodiment, the location of the leak is determined by thesensor which is the first to detect a presence of the tracer gas above athreshold level. In yet a further alternative embodiment, wherein twoadjacent sensors both report similar detections of the tracer gas, thelocation of the leak is determined to be between the location of the twoadjacent sensors, such as halfway between the sensors or closer to afirst sensor of the adjacent sensors due to a relative weighting of thevalues reported by each sensor.

It is further contemplated that the part under test might include morethan one leak. Multiple leaks may occur in the same potential leakregion or in differing potential leak regions. When sensors in differingpotential leak regions each report the detection of a leak, the abovelocation routine 686 and the rate routine 688 are conducted for eachregion. In the instance wherein multiple leaks are in the same potentialleak region, the software recognizes multiple leaks by the detection ofthe tracer gas by two non-adjacent sensors giving rise to a leakcondition. For instance, two non-adjacent sensors each record a localmaximum of tracer gas concentration or two non-adjacent sensors eachrecord the presence of the tracer gas before the intervening sensorsrecord the presence of the tracer gas.

In the case of multiple leaks it is possible to show multiple images ofthe part under test on the display at the same time, such as a splitscreen. The multiple views of the part under test is required becausethe preferred view of each sensor might be a different image or at leastone of the sensors corresponding to a leak is not visible in thepreferred image of the other sensor.

Leak rate routine 688 is configured to determine the leak rate of theidentified leak. As represented by block 696, for the sensor arraydetecting a leak the readings from each sensor associated with thatsensor array is summed and then averaged. Further, this average sensorreading is monitored over time and an average rate of change in theaverage sensor reading is calculated, as represented by block 698. In atypical leak testing situation the testing cycle and leak size are suchthat the rate of change of average sensor readings is generally linear.As such, determining the slope of a line approximating the averagesensor readings over time approximates the leak rate.

The rate of change in the average sensor readings is scaled to leak rateunits, as represented by block 700. In one example, the scaling isaccomplished by comparing the determined slope rate from the block 698and slope rates for known leaks taking into account the accumulationvolume of the fixture containing the sensors, such as fixture 133. Therate of change in the average sensor readings is directly proportionalto the leak rate of the leak and inversely proportional to the volume ofthe accumulation volume. Further, the leak rate is displayed on the partpicture or image along with the leak location determined by thelocalization routine 686. In one example, the leak rate is shown as anumeric value proximate to the leak location. In another example, theleak rate is simulated by the selection of the leak graphic to use tosimulate the leak (see FIG. 13B). For example, a graphic showing a largeleak emanating from the leak location is used for a high leak rate whilea graphic showing a small leak emanating from the leak location is usedfor a small leak rate.

Referring to FIGS. 11 and 12, example sensor output corresponding to theleak testing of part 136 with leak testing apparatus 100 is shown. Forthe example shown in FIGS. 11 and 12, a known leak 144 was introducedinto the part in the vicinity of potential leak region 134. Known leak144 was created by in part 136 by inserting a calibrated leak standardthrough part 136. Further, known leak 144 was sized to have a known leakrate equal to 0.1 scc/min (standard cubic centimeters per minute). Inorder to test leak testing software 600, the tracer gas is provided tointerior 142 of part 134 through a valve such that the response time ofsystem 100 can be determined.

FIG. 11 provides the individual sensor readings over time for five ofthe sixteen sensors positioned proximate to the potential leak region.The five selected sensors correspond to the four sensors closest to leak144 and a sensor distal to leak 144. It should be noted that sixteensensors exceeds the twelve sensors 132 a–l illustrated in FIGS. 3–5. Assuch, the results shown in FIG. 11 should be able to provide a moreaccurate location of leak 144 than the results of the twelve sensorarrangement shown in FIGS. 3–5.

Looking at FIG. 11, the sensor denoted as sensor 13 shows the firstdetection of the tracer gas and also exhibits the highest recordedconcentration of the tracer gas as represented by data series 160. Thesensors denoted as sensors 12, 14, and 15 are proximate to sensor 13 anddenoted by data series 162, 164, and 166, respectively. Each of sensors12, 14, and 15 detect the presence of the tracer gas slightly aftersensor 13 and each of sensors 12, 14, and 15 detect lower concentrationsof the tracer gas than sensor 13. As such, the location of leak 144 isproximate to sensor 13. However, it should be noted that the strongresponse of sensor 14 and the similar responses of sensors 12 and 15suggests that the leak is positioned roughly halfway between sensors 13and 14. Further, data series 168 corresponding to the sensor denotedsensor 5 which is distally positioned relative to sensor 13 is includedto demonstrate that sensors farther from the location of leak 144 lag inthe detection of the tracer gas and the measured concentration of thetracer gas over sensors that are more proximate to leak 144 such assensors 12, 14, and 15.

Referring to FIG. 12, two data series 170 and 172 are shown. Data series170 corresponds to the turning on of leak 144, represented by portion174 of series 170, and the turning off of leak 144, represented byportion 176 of data series 170. Leak 144 is turned on by introducingtracer gas to interior 142 of part 136 through a valve and is turned offby shutting the valve. Data series 172 corresponds to the average valueof the concentration of tracer gas for all of the sensors in the sensorarray over time. Looking at FIG. 12, the response time of the system isvery good. Within approximately three seconds the linear region 180 ofdata series 172 is developing suggesting that for a leak the size ofknown leak 144 the system is capable determining the leak rate withinapproximately three to five seconds. Further, the region 180 of series172 is very linear, suggesting that the slope of region 180 will providea good approximation of the leak rate of leak 144.

Returning to FIG. 10, the test timer takes precedence over localizationroutine 686 and rate routine 688. As such, when the test timer hasexpired, a stop command is issued to the sensors, as represented byblock 682. Further, a final leak rate is calculated and sent to the PLC,as represented by block 684. Alternatively the final leak rate is madeavailable to additional devices on network 122.

SENSOR APPARATUS FOR THE DETECTION OF A GAS

Referring to FIG. 14, a sensor apparatus 300 is shown. Sensor apparatus300 is configured to detect the presence of a gas, such as a tracer gasand to provide an appropriate output to communicate the detection of thepresence of the gas. In a first application sensor apparatus isconfigured to detect the presence of a tracer gas, such as helium orhydrogen, in a leak testing application. In a second application sensorapparatus 300 is configured to detect the presence of a gas, such ashelium or hydrogen, and to be incorporated into the design of acomponent as a safety sensor, example components includes automobiles,trucks, aircraft, boats, and subsystems thereof such as fuel systems,exhaust systems, passenger cabin systems and cargo systems.

Sensor apparatus 300 in one example is capable of detectingconcentrations of Helium, a tracer gas, in the range of about 0 ppm(parts per million) to about 5000 ppm and having a resolution of about25 ppm. In another example sensor apparatus 300 is capable of detectingconcentrations of Helium, a tracer gas, in the range of about 0 ppm toabout 5000 ppm and having a resolution of about 5 ppm. In yet anotherexample, sensor apparatus 300 is capable of detecting concentrations ofHelium exceeding about 5000 ppm.

Sensor apparatus 300 is capable of operating in one of two modes ofoperation. In a first mode of operation, sensor apparatus 300 is aself-contained sensor apparatus or a self-contained leak testingapparatus and provides an indication to the operator of the detection ofthe gas, such as the tracer gas, by sensor apparatus 300. In a secondmode of operation, sensor apparatus 300 provides a signal to a remotecontroller, the signal including information related to the detection ofthe gas such as the tracer gas by sensor apparatus 300. Both modes ofoperation are described in detail below. In one example of the secondmode of operation, sensor apparatus 300 is a networkable sensor thatprovides a signal to the remote controller over a network.

When sensor apparatus 300 is capable of operating in both modes ofoperation, although not necessarily both modes at the same time, sensorapparatus 300 is a dual mode sensor apparatus or a dual mode leakdetection apparatus. However, it is within the scope of the inventionthat sensor apparatus 300 is configured to only operate in either thefirst mode of operation, see generally sensor apparatus 300′ in FIG. 15,or the second mode of operation, see generally sensor apparatus 300″ inFIG. 16.

Referring back to FIG. 14, sensor apparatus 300 is a dual mode leakdetection apparatus and comprises a controller 302 connected, eitherdirectly or through additional components, to a sensor 304, a powersupply 306, an indicator 308 and an I/O interface 310. Controller 302,sensor 304, power supply 306, and indicator 308 are enclosed in ahousing 312. However, indicator 308 is at least viewable from theexterior of housing 312 and I/O interface 310 is accessible from theexterior of housing 312. Further, a sensing element or transducer 314 ofsensor 304 is accessible from the exterior of housing 312 and ispositioned generally proximate to the exterior of housing 312. As such,sensor apparatus 300 does not require that the gas to be tested for thepresence of the tracer gas be drawn to or past an internal sensingelement.

As explained in more detail below, sensor 304 is configured to detectthe presence of a gas, such as a tracer gas, and to provide a sensingsignal to controller 302, the sensing signal being indicative of thepresence or absence of the tracer gas and the amount or magnitude oftracer gas detected. In one example the sensing signal is proportionalto the concentration of the detected tracer gas. Power supply 306 isconfigured to provide power to controller 302, sensor 304, indicator308, and/or I/O interface 310. Indicator 308 is configured to provide anindication to the operator of sensor apparatus 300 of the detection ofthe tracer gas and/or the amount of tracer gas detected. I/O interface310 is configured to provide an output signal to an external device, theoutput signal being representative of the detection or lack of detectionof the tracer gas and/or the amount of tracer gas detected. Furthersignals are also contemplated, such as an error signal or a sensorstatus signal. In one embodiment I/O interface 310 is configured to linksensor apparatus 300 to a network.

Controller 302 is configured to receive the sensing signal from sensor304 and to analyze or make additional determinations based on thesensing signal from sensor 304. Further, controller 302 is configured toprovide an indication signal to indicator 308, the indication signalbeing representative of the detection or lack of detection of the tracergas and/or the amount of tracer gas detected, or controller 302 isconfigured to provide an I/O signal to I/O interface 310, the I/O signalbeing representative of the detection or lack of detection of the tracergas and/or the amount of tracer gas detected, or controller 302 isconfigured to provide both an indication signal to indicator 308 and anI/O signal to I/O interface 310.

Referring to FIG. 15, sensor apparatus 300′ is shown. Sensor apparatus300′ is generally similar to sensor apparatus 300 when sensor apparatus300 is configured to operate in the second mode of operation. As such,like numerals are used for components that are common to both sensorapparatus 300 and sensor apparatus 300′. Sensor apparatus 300′ providesa signal to a remote controller (not shown), the signal includinginformation related to the detection of the gas by sensor apparatus 300.In one example, sensor apparatus 300′ is configured to be linked to anetwork. As such, sensor apparatus 300′ is generally similar to sensorapparatus 300 expect that an indicator, such as indicator 308 is notneeded. In addition since sensor apparatus 300′ is connected to a remotecontroller through I/O interface 310, the power needed by controller 302and sensor 304 can be provided through I/O interface 310 instead ofpower supply 306. Alternatively, power supply 306 is included in sensorapparatus 300′ in situations wherein a remote power supply is notavailable, such as a wireless network. Further, the electronics ofsensor apparatus 300′, although generally similar to the electronics ofsensor apparatus 300 may be simpler at least due to the fact that sensor300′ does not need to supply an analog output, does not need to controlan indicator, and does not need to control a power supply.

Referring to FIG. 16, sensor apparatus 300″ is shown. Sensor apparatus300″ is generally similar to sensor apparatus 300 when sensor apparatus300 is configured to operate in the first mode of operation whichcorresponds to a self-contained sensor apparatus that provides anindication to the operator of the detection of the tracer gas by sensorapparatus 300. As such, like numerals are used for components that arecommon to both sensor apparatus 300 and sensor apparatus 300″ Sensorapparatus 300″ is generally similar to sensor apparatus 300 except thatan I/O interface, such as I/O interface 310 is not required. Further,the electronics of sensor apparatus 300″, although generally similar tothe electronics of sensor apparatus 300 can be simpler at least due tothe fact that the I/O interface is not required and the sensor does notneed to configure data and information for transmission over a network.

Referring to FIG. 17, one embodiment of a dual mode sensor apparatus 450is shown. Sensor apparatus 450 is generally similar to sensor apparatus300 and comprises a controller 452, a sensor 454, a power supply 456, anindicator 458, and an I/O member or interface 460 each being generallysimilar to controller 302, sensor 304, power supply 306, indicator 308,and I/O member or interface 310 of sensor apparatus 300, respectively.Sensor apparatus 450 further comprises a programming input 462, whichincludes a series of inputs 464 and is configured to provide programmingsignals to controller 452 to modify the configuration of controller 452or a parameter value stored in or accessed by controller 452. In oneexample, programming unit 452 is used to modify the network ID assignedto sensor apparatus 450 for use with a CAN network.

Sensor 454 of sensor apparatus 450 comprises a thermal conductivitysensor 466 and associated sensor circuitry 468 including an amplifiercircuit 470. Thermal conductivity sensor 466 comprises a sensing elementor transducer 467 (shown in FIG. 18) such as a membrane (not shown)which is heated above ambient temperature, a measuring resistor orseries of resistors 472 which measure the temperature of the membraneand an ambient temperature reference resistor or series of resistors 474which compensate for ambient temperature changes. As shown in FIG. 18sensing element or transducer 467 is positioned on the exterior ofsensor 466. In the illustrated embodiment, thermal conductivity sensor466 is Model No. MTCS-2202, available from Microsens SA located at RueJaquet-Droz 1, CH-2007 Neuchatel, Switerland. Alternate sensors includeother suitable thermal conductivity sensors, acoustic wave transducers,optical feedback transducers, and other suitable sensors capable ofdetecting the presence of the tracer gas.

Thermal conductivity sensor 466 measures the presence or concentrationof a tracer gas by comparing the resistance of measuring resistor 472,which is a measure of the temperature of the membrane, and theresistance of reference resistor 474. Gases that have a lower thermalconductivity than air cause a change in the surface temperature of thesensor membrane and thus a change in the resistance of measuringresistor 472. As such, when the tracer gas is either helium or hydrogenthe presence of either helium or hydrogen adjacent the sensor membranecauses a change in the surface temperature of the sensor membrane andtherefore a change in the resistance of measuring resistor 472. Further,as the concentration of either helium or hydrogen adjacent the sensormembrane increases the resistance of measuring resistor 472 changesfurther.

The illustrated sensor circuitry 468 including amplifier 470 arerecommended by the manufacturer of thermal conductivity sensor 366,Microsens SA. In alternate embodiments, variations of sensor circuitryare contemplated. The output of amplifier 470 corresponds to the sensingsignal of sensor 454 and is provided to controller 452 over connection473. In one example the sensing signal is proportional to theconcentration of the detected tracer gas. The voltage value of theoutput of amplifier 470 is directly dependent on the resistance of themeasuring resistor 472. As such, the detection of either helium orhydrogen by measuring resistor 472 will result in a decrease of theoutput voltage of amplifier 470.

Power supply 456 comprises a power source 474 represented by thedesignation “5 VDC” and a voltage regulator 476. It should be noted thatthe designation “5 VDC” is shown multiple times in FIG. 17 forconvenience and that each instance is signifying a connection to powersource 474. Power source 474 in one exemplary embodiment is a portablepower source, such as a battery. Power source 474, in another exemplaryembodiment, is an external power source such as the output of an ACadapter connected to a standard electrical outlet. Further, power source474, in yet another embodiment, is an external power supply, whichprovides power to sensor apparatus 450 through I/O interface 460.

Voltage regulator 476 is configured to provide a generally constantvoltage source to sensor 454 and controller 452. In the illustratedembodiment, voltage regulator 476 includes a circuit chip 477 Model No.ADR421, which is available from Analog Devices located at One TechnologyWay, P. O. Box 9106, Norwood, Mass. 02062-9106.

Controller 452, in the illustrated embodiment, includes aMicroConverter®, Model No. AduC834, available from Analog Devices.Controller 452 is a programmable device and includes a program memory(not shown) and a data memory (not shown). In the present inventioncontroller 452 is configured to receive the sensing signal from sensor454 over connection 473 and to analyze the sensing signal and/or makefurther determinations based on the sensing signal and the instructionsor program stored in controller 452. In one example, controller 452digitizes the sensing signal from sensor 454 and scales the sensingsignal to generate an output signal to provide to I/O interface 460. Inone example, the output signal is an analog signal generated by adigital to analog converter (D/A). In another example the output signalis a digital signal. Further, in one example, controller 452 generatesan indication signal to provide to indicator 458.

Indicator 458, in the illustrated embodiment comprises a first lightemitting diode (“LED”) 478 and a second LED 480. LED 478 provides alight visible from the exterior of sensor apparatus 450 having a firstcolor, such as green. The green light of LED 478 is provided in responseto receiving a first indication signal from controller 452 correspondingto a power on state of sensor apparatus 450. As such, LED 478 provides avisual cue to the operator of sensor apparatus 450 that sensor apparatus450 is receiving power and is functional. In an alternative embodiment,the first LED is controlled by the controller to flash during a warm-upperiod of the sensor apparatus and to provide a steady signal when thesensor apparatus is ready for testing.

LED 480 provides a light visible from the exterior of the housing ofsensor apparatus 450 having a second color, such as red. The red lightof LED 480 is provided in response to receiving a second indicationsignal from controller 452 corresponding to the detection of thepresence of the tracer gas by the sensor apparatus 450. As such, LED 480provides a visual cue to the operator of sensor apparatus 450 that thetracer gas has been detected. In a leak testing application LED 480provides a visual cue to the operator that the part under test has aleak in the vicinity of sensor 454. In another example LED 480 is abi-color LED, such as Model No. 591-3001-013 available from DialightCorporation located at 1501 Route 34 South Farmingdale, N.J. 07727. Thewavelength emitted by bi-color LED 480 is dependent on the signalprovided to LED 480. For instance, the wavelength can be varied from agenerally green wavelength to various shades of a generally orangewavelength and up to a generally red wavelength. As such, in one examplebi-color LED 480 provides a visual cue to the operator of sensorapparatus 450 of the concentration of detected tracer gas (green for lowconcentrations up to red for higher concentrations). In another example,bi-color LED 480 emits a green wavelength for low concentrations and ared wavelength for concentrations exceeding a threshold value. In analternative embodiment, the second LED is controlled by the controllerto flash during a testing period of a leak testing application of thesensor apparatus, to provide a steady signal when the presence of thetracer gas is detected by the sensor, and not emit light if the testingperiod concludes without the detection of the tracer gas.

Referring to FIGS. 19 and 20, an exemplary embodiment of sensorapparatus 450 is shown including a housing 496. Housing 496 isconfigured to enclose controller 452, sensor 454, power supply 456 (ifincluded), and indicator 458. Further housing 496 is configured toenclose a portion of member 460, such as CAN transceiver 492, CANcontroller 494, and RS-485 transceiver 490. However, as shown in FIG.19, sensing element or transducer 467 of thermal conductivity sensor 466is accessible from the exterior of housing 496 and is positionedgenerally proximate to the exterior of housing 496. Further, as shown inFIG. 20, indicator 458 is at least viewable from the exterior of housing496.

As shown in FIGS. 19 and 20, a first portion 497 of housing 496 isconfigured to couple housing 496 to another component, such as fixture133 shown in FIG. 3 in connection to a leak testing application. In theillustrated embodiment first portion 497 is threaded such that firstportion 497 may be threaded into a threaded aperture (not shown). A nut498 is shown threaded onto first portion 497. Nut 498 assists incontrolling the degree of engagement between first portion 497 and thethreaded aperture (not shown). A second portion 499 of housing 496configured to be coupled by a tool. In the illustrated embodiment,second portion 499 is faceted such that second portion 499 may begripped by a wrench to aid in the engagement or disengagement of firstportion 497 with the threaded aperture.

Referring back to FIG. 17, I/O interface 460, in the illustratedembodiment, is configured to provide one of three outputs to externaldevices. First, I/O interface 460 is configured to provide an analogoutput through connection 482 which is coupled to controller 452 throughconnection 484. In one exemplary embodiment, controller 452 provides ananalog signal scaled between 0 to 2.5 volts which is representative ofthe sensing signal from sensor 454.

Second, I/O interface 460 is configured to provide a RS-485 networkcompatible signal through connections 486 and 488. I/O interface 460includes a suitable transceiver 490 configured to comply with the RS-485standard to communicate with other devices configured to comply with theRS-485 standard over a network. RS-485 transceiver 490 is controlled bycontroller 452 through various connections. RS-485 transceiver 490, inthe illustrated embodiment, is Model No. ADM485, available from AnalogDevices.

Third, I/O interface is configured to provide a CAN network compatiblesignal through connections 486 and 488 or additional connections. I/Ointerface includes a suitable CAN transceiver 492 configured to complywith the CAN standard to communicate with other devices configured tocomply with the CAN studied over a CAN network and a suitable networkcontroller, such as CAN controller 494, configured to connect controller452 and CAN transceiver 492. CAN transceiver 492 is controlled by CANcontroller 494 and CAN controller 494 is controlled by controller 452through various connections with controller 452. CAN transceiver 492, inthe illustrated embodiment is Model No. MCP2551 and CAN controller 494is Model No. MCP2510, both available from Microchip Technology, Inc.located at 2355 West Chandler Blvd., Chandler, Ariz. 85224-6199.

The selection of which output type, analog, RS-485, or CAN, to send anoutput signal over is under the control of controller 452. In apreferred embodiment, controller 452 of sensor apparatus 450 isprogrammable to have a plug and play type functionality such thatcontroller 452 is capable of recognizing what type of network includingthe absence of a network is connected to sensor apparatus 450. Theoperation of the plug and play functionality and additional functions ofcontroller 302 are discussed with reference to FIGS. 21–24 below.

Turning to FIG. 21, a flowchart of exemplary software 500 configured toprovide a plug and play type functionality to controller 302 and toconfigure controller 302 for a leak testing application is shown.Software 500 includes a power on or reset routine 502 corresponding tofunctions to be exercised during a reset of sensor apparatus 450 or todelay the operation of further tasks until it is determined that sensor454 is warmed up and ready to detect the air surrounding sensorapparatus 450. Further, configuration steps 504 and 506 configure thesensor apparatus 450. Configuration step 504 configures controller 452including loading setup control parameters, such as network address andsensor constants. Configuration step 506 configures CAN controller 494.

Once sensor apparatus 450 is configured, software 500 checks to see if anetwork is currently connected to sensor apparatus 450, as representedby block 508. If a network is not detected, software 500 enables analogoutput to be generated by controller 452 through a D/A converter, asrepresented by block 510. The analog output is then available overconnection 482 as explained above. Further, software 500 enables a loop511 wherein the analog data from sensor 454 is converted to digital databy controller 452 and then reconverted to analog data by controller 452such that the analog data is accessible through connection 482, asrepresented by block 512. In one example, the analog data produced bycontroller 452 is different than the analog data received from sensor454 due to scaling of the data.

Loop 511 includes the steps of reading the analog data from sensor 454through an A/D converter, as represented by block 514, process and scalethe received data, as represented by block 516, and send the resultantdata if any to the D/A converter such that the data is accessiblethrough connection 482, as represented by block 518. In one example,controller 452, processes the data to determine if the data correspondsto the detection of a threshold concentration of the tracer gas andgenerates appropriate instruction to I/O member 460 and indicator 458.The threshold concentration or value in one example is programmed intosensor controller 452. In another example, the threshold value iscommunicated to sensor controller 452 from a remote device.

As loop 511 is executing, software 500 is monitoring for possiblenetwork activity indicating that a network has been connected to I/Omember 460, as represented by block 520. If no network activity isdetected, loop 511 continues. However, if network activity is detectedthe D/A output (the analog output) is discontinued, as represented byblock 522 and the network activity is tested to determine if a validnetwork is connected, as represented by block 508. If the activity isnot a valid network, the D/A output is again enabled, block 512, andloop 511 is again commenced.

Assuming a valid network is detected, software 500 checks to see if atest run flag has been set, as represented by block 524. The test runflag is an indication from either controller 452 or a device across thenetwork such as PLC 118 or computer 116 that a leak test application hasbeen initiated. Typically, a leak test application is executed for aspecific time frame. As such, sensor apparatus 450 is configured toprovide sensing data, such as a sensing signal, during the time frame ofthe leak test application.

Assuming the run test flag has been set, software 500 checks to see ifan A/D result is ready, as represented by block 526. The AID resultcorresponding to a digital signal representative of the output of sensor454. In one example, controller 452 is configured to take a reading fromsensor 454 at discrete time intervals, such as about every 100 ms. Avalue corresponding to the reading, in one example, is stored in amemory accessible by controller 452. As such, software 500 checks to seeif a current value has been stored in the memory. If a current value isnot stored, software 500 waits for a current value unless an interruptor other function needs to be performed, such as checking onboarddiagnostics, as represented by block 528. An example type of onboarddiagnostics is to check for sensor failures, as represented by block530. If a sensor failure is detected, software 500 generates andtransmits an error packet, as represented by block 532, over the networkto other devices, such as PLC 118 or computer 116.

If a current value is stored in the memory, software 500 clears thecurrent result from memory, as represented by block 534 and generatesand transmits a data packet including the current result from memory, asrepresented by block 536. The data packet is transmitted over thenetwork to other devices, such as PLC 118 or computer 116.

Software 500 although discussed in a generally progressive manner is notbound to a progressive execution. In one embodiment, software 500 checksat periodic time intervals for an interrupt routine, or a change in aparameter or flag, or the presence or absence of network activity. Afirst example interrupt routine 550 is shown in FIG. 22. Interruptroutine 550 corresponds to the reception of a network message across anetwork, such as a CAN network. The network message includes a commanddirected at sensor apparatus 450 and configured to either request orcommand sensor apparatus to perform a function. Software 500 isconfigured to interpret the command that was sent, as represented byblock 552.

Four exemplary command types are shown in FIG. 22. First, a test commandtype, as represented by block 554, corresponds to commands directed tothe initiation or cessation of a testing time period or additionalcommands related to a testing time period. A first example command, asrepresented by block 562 corresponds to a test start command. Software500 in response sets a test run flag to indicate that a test time periodhas begun, as represented by block 564. A second example command, asrepresented by block 566 corresponds to a test stop command. Software500 in response clears a test run flag to indicate that a test timeperiod has ended, as represented by block 568.

Second, an update data command type, as represented by block 556,corresponds to commands requesting that the data from the sensorapparatus be updated or verified. A first example command to update andverify data is represented by block 570. Software 500 in responsegenerates and transmits a response with the requested data, asrepresented by block 572.

Third, a read data command type, as represented by block 558,corresponds to commands requesting that the data stored in the memory ofthe sensor apparatus be read and sent. A first example command to readdata from a memory is represented by block 574. Software 500 in responsegenerates and transmits a response with the retrieved data, asrepresented by block 576.

Fourth, an update sensor command type, as represented by block 560,corresponds to commands either requesting the value of a current sensorapparatus parameter or updating a sensor apparatus parameter. A firstexample command to provide a new parameter value to sensor apparatus 450is represented by block 578. Software 500 in response generates andtransmits a response indicating that the parameter value has beenchanged, as represented by block 580.

A second example interrupt routine 582 is shown in FIG. 23. Interruptroutine 582 corresponds to a watchdog service routine. The watchdogservice routine checks to see if a RESET command is received, asrepresented by block 584 and to generate a RESET of sensor apparatus450, as represented by block 586. In one example, the RESET command isreceived across the network. In another example, the RESET command isreceived due to an operator depressing a RESET button (not shown)located on the exterior of sensor apparatus 450 or otherwise initiatinga RESET command. In yet another example, the RESET command is generatedby the controller itself, signifying that it has become unstable or isin a locked state.

A third example interrupt routine 588 is shown in FIG. 24. Interruptroutine 588 corresponds to a A/D Result Ready routine. As explained inconnection with FIG. 21, software 500 monitors to see if an A/D resultis ready corresponding to a data value from the sensor 454. Interruptroutine 588 is one mechanism by which software 500 determines that adata value corresponding to sensor 454 is available. The interruptroutine 588 includes reading A/D values, as represented by block 590,and to set a A/D result ready flag to let software 500 know that a newdata value is ready, as represented by block 592.

In one embodiment of sensor apparatus 450, all or substantially all theelectronics of sensor apparatus 450 including sensor controller 452, I/Omember 460 including the corresponding electronics for at least onenetwork type, and sensor 454 are all designed to be incorporated into acustom chip (not shown) to reduce the overall size of sensor apparatus450. In one example the thermal conductivity sensor 466 is coupled to asurface of the custom chip (not shown) containing all or substantiallyall the electronics. In another example, the thermal conductivity sensoris configured as a component of the custom chip (not shown), such thatthe sensing element or transducer of the thermal conductivity sensor ispositioned on the exterior of the chip or is accessible from theexterior of the chip. By making various connections with the leads ofthe custom chip a network such as a CAN network or an RS-485 network canbe connected to the custom chip. The reduced size of sensor apparatus450 along with the superior sensing ability of sensor apparatus 450makes sensor apparatus 450 ideal for incorporation into a component,such as an automobile, as a safety sensor. Sensor apparatus 450 willshare information with a controller (not shown) of the component torelay information and data concerning the presence or amount of a gas.

In another embodiment sensor apparatus 450 is configured to operate in asecond mode of operation similar to sensor apparatus 300′ of FIG. 15 andis designed to be incorporated into a custom chip (not shown) to reducethe overall size of sensor apparatus 450. As such, sensor apparatus 450does not include an indicator, such as indicator 458. In addition sincesensor apparatus 450 will be connected to a remote controller throughI/O member 460, the power needed at least by controller 452 and sensor454 can be provided through I/O interface 460 instead of through powersupply 476. In one example the thermal conductivity sensor 466 iscoupled to a surface of the custom chip (not shown) containing all orsubstantially all the electronics. In another example, the thermalconductivity sensor is configured as a component of the custom chip (notshown), such that the sensing element or transducer of the thermalconductivity sensor is positioned on the exterior of the chip or isaccessible from the exterior of the chip. By making various connectionswith the leads of the custom chip a network such as a CAN network or anRS-485 network can be connected to the custom chip. As stated before,the reduced size of sensor apparatus 450 along with the superior sensingability of sensor apparatus 450 makes sensor apparatus 450 ideal forincorporation into a component, such as an automobile, as a safetysensor. Sensor apparatus 450 will share information with a controller(not shown) of the component to relay information and data concerningthe presence or amount of a gas.

Referring to FIGS. 25 and 26, an exemplary embodiment of sensorapparatus 450 is shown wherein all or substantially all of theelectronics of sensor apparatus 450 are incorporated into a custom chip.Sensor apparatus 450 includes a housing 596, which is configured toenclose the custom chip (not shown) and sensor 454. Further housing 596is configured to enclose a portion I/O interface 460, such as CANtransceiver 492, CAN controller 494 which may be incorporated into thecustom chip (not shown). However, as shown in FIG. 25, sensing elementor transducer 467 of thermal conductivity sensor 466 is accessible fromthe exterior of housing 596 and is positioned generally proximate to theexterior of housing 596. Further, as shown in FIG. 26, I/O interface 460is accessible from the exterior of housing 596.

As shown in FIGS. 25 and 26, a first portion 597 of housing 596 isconfigured to couple housing 596 to another component. As shown in FIG.27, sensor apparatus 450 is positioned in several locations on acomponent 700, such as an automobile. Sensor apparatus 450 a and 450 bare coupled to a fuel system 702 of automobile 700 and sensor apparatus450 c is coupled to an exhaust system 704 of automobile 700. Sensorapparatus 450 a, 450 b, and 450 c are connected through I/O interfaces460 a, 460 b, and 460 c to a component controller 706 of automobile 700.

Although the invention has been described in detail with reference tocertain illustrated embodiments, variations and modifications existwithin the scope and spirit of the present invention as defined in thefollowing claims.

1. A sensor apparatus for detecting the presence of a leak in a partunder test, the part under test being pressurized with a gas including atracer gas, the sensor apparatus comprising: a housing; a sensorconfigured to detect the presence of the tracer gas and to generate asensing signal; at least a first portion of the sensor being containedin the housing; an I/O interface coupled to the housing, the I/Ointerface being configured to provide a first connection correspondingto an analog output and a second connection corresponding to a networkoutput both the first connection and the second connection being adaptedto connect to at least one remote device such that the analog output andnetwork output can be transmitted to the at least one remote device; anda sensor controller connected to the sensor and the I/O interface andconfigured to generate an output signal based on the sensing signalgenerated by the sensor, the sensor controller further configured todetermine if a network is present across the second connection of theI/O interface and to generate a data packet for transmission over thenetwork if the network is present, the sensor controller being containedin the housing.
 2. The sensor apparatus of claim 1, wherein the sensorincludes a thermal conductivity transducer.
 3. The sensor apparatus ofclaim 2, wherein a portion of the thermal conductivity transducer isaccessible from an exterior of the housing and is positioned proximateto the exterior of the housing.
 4. The sensor apparatus of claim 3,wherein a first portion of the exterior of the housing is configured tobe coupled to a fixture, the fixture being configured to position thesensor apparatus proximate to the part under test.
 5. The sensorapparatus of claim 1, wherein the sensor controller is configured todetect the presence of a first network and the presence of at least oneadditional network.
 6. A sensor apparatus for detecting the presence ofa leak in a part under test, the part under test being pressurized witha gas including a tracer gas, the sensor apparatus comprising: ahousing; a sensor configured to detect the presence of the tracer gasand to generate a sensing signal; at least a first portion of the sensorbeing contained in the housing; an I/O interface coupled to the housing,the I/O interface being configured to provide a first connectioncorresponding to an analog output and a second connection correspondingto a network output; and a sensor controller connected to the sensor andthe I/O interface and configured to generate an output signal based onthe sensing signal generated by the sensor, the sensor controllerfurther configured to determine if a network is present across thesecond connection of the I/O interface and to generate a data packet fortransmission over the network if the network is present, the sensorcontroller being contained in the housing, wherein the sensor controlleris configured to detect the presence of a first network and the presenceof at least one additional network, the sensor controller is configuredto provide the analog output over the first connection when neither thefirst network nor the at least one additional network are present. 7.The sensor apparatus of claim 3, wherein the sensor apparatus is astand-alone leak detection apparatus, the sensor apparatus furthercomprising a power supply positioned within the housing and coupled toat least the sensor controller and an indicator viewable from theexterior of the housing, the indicator being configured to provide anindication of the presence of the tracer gas.
 8. The sensor apparatus ofclaim 1, wherein the sensor is configured to generate the sensing signalabsent movement of the tracer gas by the sensor apparatus past thesensor.
 9. The sensor apparatus of claim 1, wherein the controllerprovides the analog output over the first connection only in the absenceof the network being present over the second connection.